1. Field of Invention
This invention relates to a system for pouring concrete building slab foundations, wherein the forms used to retain the concrete remain as part of the permanent structure and provide perimeter insulation.
2. Description of Prior Art
Heretofore in the construction of floating concrete building slab foundations, many problems and inefficiencies have been known and recognized.
The most common procedure for constructing a floating slab foundation has been to first dig an upwardly opening trench around the perimeter of the building site and secondly to erect wooden forms in end-to-end fashion, to define the periphery of the building slab. Concrete is then poured into the forms and after it has hardened, the forms are stripped away and either discarded or cleaned and transported to the next site. Perimeter insulation must then be affixed to the slab edge and overlain with a protective shield such as sheet metal or a stucco material.
A list of the tendencies and problems of this and similar procedures is as follows:
(a) Since rather short lengths of forms (approximately ten to sixteen feet) are used, extreme care must be taken as they are staked into position, to ensure their correct location, both laterally and vertically. Any waviness of the forms will result in the building slab being out of dimension and or out of level.
(b) It is difficult to affix insulation to the slab edge. Often insulation is attached to the forms prior to the casting of the concrete, but this often results in the insulation coming off of the slab edge and staying on the forms, when the forms are removed. If the insulation is attached to the hardened concrete after the removal of the forms, it involves expensive and labor intensive procedures.
(c) Various labor intensive means such as re-bar chairs must be employed to hold steel reinforcing in the proper position prior to casting of the concrete.
(d) Special configurations such as brick ledges and stem walls are particularly difficult, labor intensive, and prone to error.
(e) An unnecessary excess of concrete is often required because the interior vertical side of the footing trench tends to cave off because of sandy or unstable earth.
(f) Placement, removal, and transportation of forms results in significant costs in both labor and material.
(g) Embedded fasteners such as mudsill anchors, have to be held in correct alignment by:
(1) site constructed templates PA1 (2) fastening to the forms, which makes removal of forms difficult. PA1 (3) manually setting them into the plastic concrete, which is both inaccurate and labor intensive. PA1 (a) It is held in position by conventional wooden stakes which must be subsequently removed. PA1 (b) Stakes and mudsill anchors which extend upward from the slab surface, interfere with screeding operations while casting the concrete slab. PA1 (c) The insulated girdle is too short in its vertical dimension, and is without means to secure the additional insulating panel which is positioned below it. PA1 (d) The embedded tie means with rebar supports, positions the rebar high in the concrete footing, rather than in the lower portion where it achieves its greatest potential as reinforcement. PA1 (a) The spring clip employed for securing the panel to wooden stakes has proven to be ineffective and after this panel was made commercially available, it was simply nailed to the wooden stakes. This practice leaves holes and blemishes in the finish exterior surface. PA1 (b) Because the protective sheath only partly encases the foam core, the form panel must be made from high density and therefore high cost foam in order to achieve sufficient rigidity.
There have been a number of inventions which have addressed some of the aforementioned problems encountered in the forming of concrete building slabs. They are as follows:
(1) U.S. Pat. No. 4,202,145 Coulter et al (1980) provides for a metal leave-in-place form with internal stakes. This system offers some advantage, but makes no provision for perimeter insulation and is too elaborate to be economically feasible.
(2) U.S. Pat. No. 4,335,548 Rehbein (1982) provides for an insulating lost formwork panel with a protective sheath, but is without readily workable means for staking the panels into position or connecting panels end-to-end.
(3) U.S. Pat. No. 4,524,553 Hacker (1985) provides for a thermal insulating girdle with protective sheath and mudsill anchors, but has a number of disadvantages, which are:
(4) U.S. Pat. No. 4,711,058 Patton (1987) provides for a form comprised of a foam core and protective sheath but has the following disadvantages:
In summary, many of the drawbacks listed above in the traditional process of constructing concrete building slabs are not sufficiently addressed by the prior art, nor the traditional methodology.